Dissipation rates of iprodione and thiacloprid during tomato production in greenhouse

The behaviour of the insecticide thiacloprid and the fungicide iprodione was investigated in greenhouse tomato fruits, when both pesticides were applied in two different rates (normal dose-ND, and double dose-DD). Thiacloprid residues were below the already established EU MRLs (0.5 mg/kg) 2 and 7 days after ND and DD application, respectively. Iprodione residues were always below EU MRLs (5 mg/kg) in both application rates. The impact of storage on pesticide residues in tomatoes was also assessed. Significantly higher iprodione residue levels were observed during post harvest storage compared with those determined in fresh harvested tomatoes. Mean residue levels determined in fresh harvested tomatoes 12 days after iprodione application were 0.69 mg/kg whereas, in post harvest tomatoes stored for the same period was 0.86 mg/kg. On the contrary, no differences were noticed in thiacloprid residues between post harvest stored and fresh harvested tomatoes. Model equations that best describe the dissipation curves obtained from the experimental data of iprodione and thiacloprid in tomatoes showing different behaviour of the two pesticides. Half-life period of iprodione in ND treatment, calculated by the best fitted experimental data, (2nd order model) was 6.8 days, whilst for thiacloprid the best fitted to experimental data, model equation (R.F. 1st order model) gave a half-life of 1.9 days.